Construction and industrial workers are at high risk for work-related musculoskeletal disorders, often caused by repetitive tasks and lifting heavy loads. To reduce these work-related musculoskeletal disorders, guidelines on human strength capabilities should be followed to help mitigate injuries by reducing muscle overloading. Current solutions focus on rehabilitation and are often focused on the shoulder, elbow, and fingers, leaving the wrist vulnerable. In work-related injuries, the wrist is one of the most commonly injured body parts and is associated with high cost; both medical costs and cost due to productivity, as the median absence of work is 13 days. Injuries can be the result of bone impact forces, but more commonly muscle tissue and central nervous system damage resulting from repetitive tasks. Research shows that injuries are most common at workstations with frequent wrist deviation. Therefore, the goal of this paper is to design an orthosis to support employees in construction or industry work when working with a drill.

For the orthosis to be accepted by the users it has to be easy to use and should not limit freedom of movement. A force analysis of the wrist when holding the drill, and when using the drill against a vertical wall indicates that both the ulnar deviation and the radial deviation must be supported. To clarify which requirements are a basic necessity for the orthosis to be functional and which can be scored on functionality, they are divided into product requirements and user requirements, respectively.

Five concepts are presented to help support both the ulnar deviation and the radial deviation. Three of them are passive solutions, the other two are active. A prototype of all concepts is made and they are scored following the User Requirements utilizing a Harris Profile. During testing it is clear that the ulnar deviation support has little to no impact on the experienced muscle force. Therefore, this requirement is ignored and the orthosis ar scored with the other requirements. Both the concept using Bowden cables and the Support Arm scored well. Since the Support Arm is less complex and functional for the purpose of this research, the Support Arm is further developed.

A force analysis confirmed that the Support Arm can assist in lifting the drill by generating a configurable support force, adjustable via the spring constant or position of the attachment point. Testing the orthosis indicated that the forearm is not in line with the drill, as was expected, reducing the force on the drill. To resolve this, the attachment points of the spring and beam are angled 20 degrees to counteract the angle of the forearm compared to the drill.

The calculation in this paper are simplified, further analysis is needed to determine the effects excluded in this paper. The prototype of the orthosis should also be tested using EMG and a musculoskeletal model. This can give an indication on the effect of the orthosis on muscle activation an muscle force. More improvements of the orthosis are needed to improve user comfort and increase the force transfer. The Support Arm functions only to help lift an object. For more general wrist support and with further research, the Bowden Cable concept is promising. While more complex, the concept can help with dynamic forces to assist to the wrist movements.

In conclusion, the Support Arm orthosis effectively reduces the experienced muscle load during radial deviation when a drill is being lifted. The supporting force of the orthosis can be easily modified depending on the task. For the goal of this research, to support employees in construction and industry work when working with a drill, the Support Arm is a functional solution that can decrease the necessary muscle force and, in doing so, also decrease the bone contact forces in the wrist.